U.S. Pat. No. 4,667,546, corresponding to European Patent Publication 0,197,172, discloses a method and apparatus of the above type. In order to assure a satisfactory fracturing of the produced chips, it is necessary in the prior art that the tool oscillates periodically. Additionally, the periodic oscillations must be generated so as to produce an exactly tuned phase shift in the oscillation. Although the known method produces a reliable fracturing of the chips, it has been noted that the surface quality of work pieces produced by the just mentioned method leaves room for improvement.
The above method is also subject to certain limitations when it is applied to heavy duty machining operations, for example the reprofiling of railroad wheel sets. Machining operations of this type regardless whether above floor or under floor railroad wheel set turning machine tools are involved, make it difficult to maintain the above mentioned phase shift in the oscillation of the feed advance speed. It is difficult to maintain the required phase shift because so-called slip may occur between the wheel set and the frictional rollers which drive the wheel set. Similarly, any entraining members or lathe dogs engaging the rotating wheel set may be subject to slip so that again the required phase shift cannot be satisfactorily maintained. As a result, the desired fracturing of the chips is not assured.